''Protorosaurus'' ("first lizard") is a genus of lizard-like early

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

s. Members of the genus lived during the late Permian period in what is now Germany and Great Britain. Once believed to have been an ancestor to

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s, ''Protorosaurus'' is now known to be one of the oldest and most primitive members of

Archosauromorpha Archosauromorpha (Greek for "ruling lizard forms") is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs (such as crocodilians and dinosaurs, including birds) rather than lepidosaurs (such as tuataras, liza ...

, the group that would eventually lead to

archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...

s such as

crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

s and dinosaurs.

Description

''Protorosaurus'' grew up to in length, and was a slender, lizard-like animal, vaguely resembling a

monitor lizard Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recogn ...

, with long legs and a long neck.

Discovery

''Protorosaurus'' was one of the first fossil reptiles to be described, being initially described in Latin in 1710 by from a specimen found in Thuringia in Germany, who considered the animal to be a crocodile, and most similar to the Nile crocodile (''C. niloticus''). Over a century later, in publications in 1830 and 1832 Hermann von Meyer recognised ''Protorosaurus'' as distinct extinct reptile and gave it a formal species description, dedicating an extensive

monograph A monograph is a specialist work of writing (in contrast to reference works) or exhibition on a single subject or an aspect of a subject, often by a single author or artist, and usually on a scholarly subject. In library cataloging, ''monograph ...

to it in 1856. In 1871 Thomas Henry Huxley erected the clade Protorosauria, with ''Protorosaurus'' as the only member. The German specimens were found in the

Kupferschiefer The Kupferschiefer (German for Copper Shale, also called Copper Slate) or Kupfermergel (Copper Marl), (T1 or Z1) is an extensive and remarkable sedimentary unit in Central Europe. The relatively monotonous succession is typically and maximum th ...

a widespread unit of Late Permian (likely Wuchiapingian) age. In 1914, a new ceratopsian dinosaur found by Lawrence Lambe was again given the name ''Protorosaurus'' (in this sense meaning "before '' Torosaurus''"). When Lambe found that the name had already been used for the early archosauromorph, he renamed his ceratopsian '' Chasmosaurus''. In 1870, a new species, ''Protorosaurus huxleyi'' was described from a

railway cutting Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in Track (rail transport), tracks. In contrast to road transport, where the ...

near Middridge in

County Durham County Durham ( ), officially simply Durham,UK General Acts 1997 c. 23Lieutenancies Act 1997 Schedule 1(3). From legislation.gov.uk, retrieved 6 April 2022. is a ceremonial county in North East England.North East Assembly �About North East E ...

in northern England, in sediments belonging to the

Marl Slate The Marl Slate Formation is a geological formation in England. Despite its name, it is mostly dolomite rock. The Marl Slate Formation was formed about 273 to 259 million years ago, during the Guadalupian and Lopingian epochs of the late Pe ...

, a unit that is equivalent to the Kupferschiefer, however it was later shown that this specimen was not ''Protorosaurus'', and it was subsequently placed in the new genus '' Adelosaurus''. In 1993, a specimen of ''Protorosaurus'' was described from Quarrington Quarry also in County Durham, in sediments of the Marl Slate. This skeleton included fragments of the skull that had not previously been known. A thorough redescription of ''Protorosaurus'' was published in 2009, including a specimen with a complete skull.

Paleobiology

Stomach contents of a specimen of ''Protorosaurus'' show the presence of numerous ovules of the locally common voltzialean conifer '' Ullmannia frumentaria'', which was unexpected given its unspecialised dentiton of conical and unserrated teeth, which were assumed to represent a predatory lifestyle. Along with the coniferous ovules, several rounded pebbles were found in the body cavity, these may have functioned as

gastroliths A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In othe ...

Relationships

''Protorosaurus'' has been suggested to be closely related to ''

Czatkowiella ''Czatkowiella'' is an extinct genus of long-necked archosauromorph known from Early Triassic (Olenekian age) rocks of Czatkowice 1, Poland. It was first named by Magdalena Borsuk−Białynicka and Susan E. Evans in 2009 and the type species is ' ...

'' from the Early Triassic of Poland, but the remains of ''Czatkowiella'' are fragmentary and mixed in with those of other reptiles, so it is possible that the taxon is a

chimaera Chimaeras are cartilaginous fish in the order Chimaeriformes , known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively. At ...

. In a comprehensive analysis of "Protorosauria" in 2021, ''Protorosaurus'' was consistently recovered as the earliest diverging member of

. The cladogram below follows an analysis by Ezcurra (2016), and highlights the position of ''Protorosaurus'' among other early archosauromorph reptiles.

Paleoenvironment

The Kupferschiefer and equivalent Marl Slate is a marine unit that forms part of the

Zechstein The Zechstein (German either from ''mine stone'' or ''tough stone'') is a unit of sedimentary rock layers of Middle to Late Permian (Guadalupian to Lopingian) age located in the European Permian Basin which stretches from the east coast of Englan ...

, a sequence of rocks formed on the edge of the Zechstein Sea, a large inland shallow sea that existed in Northern Europe during the Late Permian. The environment at the time of deposition is considered to have been semi-arid. The terrestrial flora of the Zechstein is dominated by conifers, with

seed ferns A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm pl ...

also being common, while taeniopterids, ginkgophytes and sphenophytes are rare. Other terrestrial vertebrates found in the Kupfershiefer and lower Zechstein include the gliding

weigeltisaurid Weigeltisauridae is a family of gliding neodiapsid reptiles that lived during the Late Permian, between 258 and 252 million years ago. Fossils of weigeltisaurids have been found in Madagascar, Germany, Great Britain, and Russia. A possible weigelt ...

reptiles '' Weigeltisaurus'' and '' Glaurung,'' the

pareiasaur Pareiasaurs (meaning "cheek lizards") are an extinct clade of large, herbivorous parareptiles. Members of the group were armoured with scutes which covered large areas of the body. They first appeared in southern Pangea during the Middle Permian, ...

Parasaurus ''Parasaurus'' (meaning "near lizard") is a genus of pareiasaur known from fossils collected in the Kupferschiefer in Germany (Hesse, Thuringia and Lower Saxony), dating to the Late Permian (Wuchiapingian). The type species, ''Parasaurus geinit ...

,'' the

cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...

'' Procynosuchus,'' and indeterminate

captorhinids Captorhinidae (also known as cotylosaurs) is an extinct family of tetrapods, traditionally considered primitive reptiles, known from the late Carboniferous to the Late Permian. They had a cosmopolitan distribution across Pangea. Description C ...

, dicynodonts, and

dissorophid Dissorophidae is an extinct family of medium-sized, temnospondyl amphibians that flourished during the late Carboniferous and early Permian periods. The clade is known almost exclusively from North America. History of study Dissorophidae is a ...

temnospondyls.

References

{{Taxonbar, from=Q134702 Prehistoric reptile genera Lopingian life Prehistoric archosauromorphs Permian reptiles of Europe Permian Germany Fossils of Germany Kupferschiefer Fossil taxa described in 1830 Taxa named by Christian Erich Hermann von Meyer